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Answer the following. (Class 10 Science 2025, Q34A)

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ScienceCBSE Class 10 · Board exam 2025, set 31/5/1 · 5 marks · Long answer

CBSE Class 10 Science 2025: question 34(A)

Set in the CBSE Class 10 board exam of 2025, paper 31/5/1, section D, question 34(A), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q34(A) · 5 marks · Long answerCarbon and its Compounds

Answer the following.

  1. (a)

    What is meant by the term homologous series of carbon compounds? Write molecular formula of any two consecutive members of homologous series of ketones.

    0 marks
  2. (b)

    Write chemical equation of the reactions of ethanoic acid with (i) Sodium hydroxide and (ii) Ethanol (in the presence of an acid); giving the name of the products in each case.

    0 marks
  3. (c)

    Draw the structure of the molecule of benzene.

    0 marks

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 31/5/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Members of a homologous series differ by one CH₂ unit; the smallest ketone has 3 carbons.

Hint 2

An acid with a base gives salt and water; an acid with an alcohol gives an ester.

Hint 3

Benzene is a six-membered ring with three alternating double bonds.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. (a) A homologous series is a series of carbon compounds that have the same functional group substituting for hydrogen in a carbon chain. They have the same general formula and similar chemical properties, and successive members differ by a unit.

    1 mark

  2. (a) Two consecutive ketones: propanone () and butanone ().

    1 mark

  3. (b)(i) . Product: sodium ethanoate (sodium acetate) and water.

    1 mark

  4. (b)(ii) . Product: ethyl ethanoate (an ester) and water (esterification).

    1 mark

  5. (c) Benzene, : six carbon atoms joined in a hexagonal ring with alternating single and double bonds (C=C, C–C, C=C, C–C, C=C, C–C). Each carbon carries one hydrogen atom by a single bond.

    1 mark

Answer: (a) Series with same functional group/general formula and similar properties; C₃H₆O and C₄H₈O; (b)(i) sodium ethanoate, (ii) ethyl ethanoate; (c) hexagonal ring of 6 C with alternate double bonds, one H on each C.

Where the marks are

  • Definition of homologous series (1 mark)
  • Two consecutive ketones, e.g. C₃H₆O and C₄H₈O (½ + ½ mark)
  • Equation with NaOH, naming sodium ethanoate (1 mark)
  • Esterification equation, naming ethyl ethanoate (1 mark)
  • Correct structure of benzene (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Carbon and its Compounds, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 31/5/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.